Submerged geothermal power generation system
A subterranean geothermal power generation system is disclosed herein, comprising a closed cavity, a temperature differential mechanical power generation device, an electric power generation device and a heat conduction module. The mechanical power generation device with a heat source end and a cold source end and the electric power generation device are integrated into the cavity. The heat source end is exposed from the cavity for contacting with a heat source in the well; the cold source end and the electric power generation device are located in the cavity. A heat conduction fluid is filled into the cavity, the heat conduction module extends from the cavity to the outside of the well. Accordingly, a temperature difference between the cold source end and the heat source end is created to enable the mechanical power generation device to mechanically drive the electric power generation device to generate electricity.
The present invention relates to a subterranean geothermal power generation system, in particular to a power generation equipment that utilizes an underground heat source such as geothermal energy or a hot spring to generate electricity.
Description of the Related ArtGeothermal power generation is low-carbon or even zero-carbon clean renewable energy helpful in reducing environmental pollution and mitigating global warming, and the most important feature of geothermal power generation lies in grid stability that green energy such as wind and solar energy lacks. Geothermal power generation which is not affected by the weather and can stably generate electricity 24 hours a day has a small footprint, a low land utilization rate and a low impact on environmental ecology, and hence geothermal power generation is being developed in full swing around the world.
A related prior art of a geothermal power generation system is disclosed in PCT Publication No. WO2019/067618, entailed “Systems and Methods of Generating Electricity Using Heat from within the Earth”, in which the technique of utilizing a Stirling engine is disclosed in the embodiment shown in
Also, another prior art is shown in US Patent Publication No. 2008/0209904, entitled “Systems and Methods for Generating Electricity Using a Stirling Engine.” In
Yet another prior art is shown in PCT Patent Publication No. WO2010/102379, entitled “Heat Engine Apparatus for USE in Wellbore and Related Method”, which discloses a heat engine (for example, a Stirling engine) is disposed in a wellbore, and a heat exchange fluid is circulated forcibly by a pump, wherein after the heat exchange fluid is heated at the bottom of the well, the heat exchange fluid is pumped by the pump to a hot end of the heat engine for heat exchange. Next, the heat exchange fluid is pumped to a heat exchange fluid reservoir on the earth ground and then flows into another heat exchanger for cooling; after the heat exchange fluid is cooled, the heat exchange fluid is pumped to a cold end of the heat engine for heat exchange; finally, the heat exchange fluid is pumped to the bottom of the well again for heating, thereby forming a circulation loop. However, this prior art also has to consume a large amount of energy for forced circulation of the heat exchange fluid, circulation pipes are long and complicated, and construction work is difficult. Moreover, hot spring water tends to cause the pipelines to be clogged and corroded, thereby increasing equipment maintenance costs and reducing its service life.
As can be seen from the above, it is necessary to dig a deep hole to obtain a heat source for the existing geothermal power generation systems, construction work requires much labor, and uninterrupted circulation of a heat conduction fluid is necessary for generating temperature difference by heating and cooling the heat conduction fluid. Since the forced circulation of the heat conduction fluid consumes a large amount of energy so that the cost of power generation may be greater than the benefit of power generation, they are never put into commercial operation. In addition, construction cost is expensive, and repair and maintenance are inconvenient.
SUMMARY OF THE INVENTIONThe main object of the present invention is to provide a subterranean geothermal power generation system which is capable of automatically and stably generating electric power all the times and has no need of additional energy for maintaining the system operation. Electricity generated is completely output with excellent power generation efficiency; no groundwater extraction is required, it has a small footprint and a low impact on the environment; the entire generator set is placed into a well and can be easily hoisted out when maintenance or repair is required, so equipment cost, construction cost and maintenance cost are inexpensive.
In order to achieve the above object, a subterranean geothermal power generation system of the present invention mainly comprises a closed cavity, a temperature differential mechanical power generation device, an electric power generation device, a heat conduction module and a heat conduction fluid; the closed cavity is placed into a well which provides a heat source; the temperature differential mechanical power generation device includes a heat source end and a cold source end and is disposed in the closed cavity, wherein the heat source end is exposed from the closed cavity and brought into contact with the heat source, and the cold source end is located in the closed cavity; the electric power generation device is mechanically connected to the temperature differential mechanical power generation device and housed in the closed cavity, wherein when a temperature difference between the heat source end and the cold source end of the temperature differential mechanical power generation device reaches a specific value, the temperature differential mechanical power generation device mechanically drives the electric power generation device to generate electricity; the heat conduction module includes a first end and a second end, wherein the first end is located in the closed cavity, and the second end extends out of the well; the heat conduction fluid is filled into the closed cavity, and the cold source end of the temperature differential mechanical power generation device, the electric power generation device and the first end of the heat conduction module are immersed in the heat conduction fluid.
As can be seen from the above, in the present invention, the entire generator set is integrated in the single closed cavity and can be hoisted and placed into the well, wherein the heat source end of the temperature differential mechanical power generation device is exposed from the closed cavity and brought into contact with the heat source in the well; the cold source end and the electric power generation device are located in the closed cavity; and by means of the heat conduction liquid and the heat conduction module, the temperature in the closed cavity is maintained at the same temperature as the temperature outside the well, thereby forming a significant temperature difference between the cold source end and the heat source end for operation of the temperature differential mechanical power generation device. Accordingly, the present invention has no need of additional energy for assisting the operation of the system, is capable of automatically generating electric power all the times and not affected by the weather; and the present invention has no need of extraction of heat source (such as hot spring water), has a low impact on the environment and can be used for sustainable power generation; moreover, the entire generator set can be hoisted and placed into the well after the well is dug and can be directly hosted out when maintenance is required, installation and maintenance are convenient, and the equipment and construction costs are inexpensive.
Before a subterranean geothermal power generation system according to the present invention is described in detail in the embodiments, it should be noted that in the following description, similar components will be designated by the same reference numerals. Furthermore, the drawings of the present invention are for illustrative purposes only, they are not necessarily drawn to scale, and not all details are necessarily shown in the drawings.
Reference is made to
Furthermore, the generator set GS of this embodiment mainly includes a closed cavity 2, a temperature differential mechanical power generation device 3 and an electric power generation device 4, wherein the temperature differential mechanical power generation device 3 of this embodiment adopts a Stirling engine, but the present invention is not limited to this, and other heat engines capable of generating mechanical power by utilizing temperature difference can be applied hereto. The temperature differential mechanical power generation device 3 is disposed in the closed cavity 2 and includes a heat source end 31 and a cold source end 32, the heat source end 31 is exposed from the closed cavity 2 and brought into contact with a heat source Sh (hot spring water or high-temperature soil) in the hot spring well W, and the cold source end 32 is located in the closed cavity 2.
Since the heat source end 31 of the temperature differential mechanical power generation device 3 of this embodiment is immersed in the hot spring for a long time, corrosion or scaling inevitably occurs; for this reason, the heat source end 31 of this embodiment adopts a stainless steel housing and is covered with a nickel alloy 625 (Inconel®625), which has good corrosion resistance and can resist scaling and oxidation especially at high temperature. In addition, the outer surface of the heat source end 31 can also be coated with carbon nitride, boron nitride or other materials containing carbon or boron to further prevent or suppress scaling and corrosion.
The housing of the cold source end 32 of the temperature differential mechanical power generation device 3 in this embodiment is provided with fins 33 for promoting heat exchange, thereby facilitating the heat exchange rate between the cold source end 32 and a heat conduction fluid L. The electric power generation device 4 of the present embodiment is a linear alternating current generator, which is mechanically connected to the temperature differential mechanical power generation device 3 and is housed in the closed cavity 2. When the temperature difference between the heat source end 31 and the cold source end 32 of the temperature differential mechanical power generation device 3 reaches a specific value, usually about 45° C. to 55° C. or higher, the temperature differential mechanical power generation device 3 automatically operates and mechanically drives the electric power generation device 4 to generate and output electricity.
In addition, the heat conduction fluid L which may be pure water is filled into the closed cavity 2. However, in this embodiment, a nanofluid having the features such as high heat capacity and high thermal conductivity is used and is mainly composed of two components, i.e. nanoparticles and a base fluid, wherein the nanoparticles may be of metal, metal oxide, carbide, carbon nanotubes, graphene, wherein nano metal particles are preferably of magnesium; the base fluid may be water, glycol, oil, wherein the oil is preferably synthetic heat conduction oil Therminol®. Furthermore, other additives, such as anti-corrosion additives and dispersants to resist agglomeration of nanoparticles, may also be added.
Regarding the heat conduction module 5, the present embodiment adopts a heat pipe, which includes a first end 51 and a second end 52, wherein the first end 51 is located in the closed cavity 2, and in order to increase the heat transfer effect, the first end 51 is arranged in a spiral shape along the length direction of the closed cavity 22 around the cold source end 32 of the temperature differential mechanical power generation device 3 and the electric power generation device 4, thereby obtaining a better heat exchange effect. It should be particularly noted that the heat conduction module 51 of the present invention is not limited to the heat pipe and may also be a heat conduction member having an excellent heat conduction effect such as a thermosiphon, a thermal conductive graphite sheet, and a vapor chamber.
Reference is made to
Reference is made to
On the other hand, in order to achieve anti-corrosion, anti-oxidation and anti-scaling, a thermally sprayed aluminum coating is specially applied to the outer surface of the heat pipe section 50 in this embodiment; furthermore, the heat pipe section 50 is externally covered with a heat insulation material 58, in this embodiment, two-phase and three-phase epoxy resin composite foam plastics are used as the heat insulation material 58, and of course, other materials such as polyurethane heat insulation material, heat insulation cotton and polylactic acid foam material can also be used. In other embodiments, in order to further improve the anti-corrosion, anti-scaling and heat insulation effects of the heat insulation material 58, a nano coating such as a coating of 30% acrylic resin water and 70% nano material, may be additionally applied, wherein the nano material may be multi-walled carbon nanotubes (MWCNTs). Similarly, the outer surface of the closed cavity 2 is also covered with the same heat insulation material 58 so as to prevent the high temperature in the hot spring well W from affecting the temperature of the closed cavity 2.
Reference is made to
Reference is made to
In addition, the working fluid in the heat conduction module 5 may be discharged as the evacuation module 7 operates, so in this embodiment, a fluid reservoir 73 is provided at the second end 52 so that working fluid can be added in time. reference is further made to
It is additionally explained that, as shown in
Reference is made to
As can be seen from the above, the main controller 80 can obtain various temperature and pressure parameters through the aforementioned sensors so as to determine whether the system or the environment is in a normal state. Furthermore, the upper fluid level detector 511 and the lower fluid level detector 512 are used to detect the quantity of the working fluid in the heat conduction module 5; when the quantity of the working fluid is insufficient, that is, the working fluid cannot be detected by the lower fluid level detector 511, the main controller 80 can control the switch of the fluid reservoir 73 to automatically replenish the working fluid; and when the working fluid is detected by the upper fluid level detector 511, that is, the quantity is sufficient, the main control 80 turns off the switch of the fluid reservoir 73.
This embodiment uses a non-contact fluid level detector, such as a non-contact capacitive sensor, which is capable of converting variable medium (such as fluid level) into a processable signal, and its principle is that when the working fluid is close to a sensitive surface of the capacitive sensor, the capacitance value changes, that is, the electric field around the active region changes, thereby forming a detection signal. Of course, the present invention can also use an electromagnetic induction fluid level detector, which has an electromagnetic coil that generates a magnetic field, and an electrode that captures an electromotive force (voltage), and when the working fluid passes through the magnetic field, an induced electromotive force is generated, thereby forming a detection signal.
Therefore, the non-contact fluid level detector used in this embodiment is not affected by the temperature, pressure, density, or viscosity of the liquid and is capable of detecting liquids containing contaminants (solids or gases) without causing liquid pressure loss, has no movable parts, and has high reliability. However, the present invention is not limited to the non-contact capacitive sensor, and other types of contact or non-contact fluid level detectors, such as photoelectric sensors, can also be used.
Moreover,
In addition, it is worth mentioning that the top surface of the closed cavity 2 in this embodiment is provided with a hoisting ring 21, which can be used for hoisting the generator set GS; for example, when the system is installed, the generator set GS can be hoisted and placed into the hot spring well W by means of the hoisting ring 21; and when maintenance or repair is to be carried out, the generator set GS can also be hoisted out in a hoisting manner, so this is quite convenient.
Reference is made to
Reference is made to
The above-mentioned embodiments are only examples for the convenience of description, and the scope of the present invention should be defined by the following claims, rather than limited to the above-mentioned embodiments.
Claims
1. A subterranean geothermal power generation system, comprising:
- a closed cavity, placed into a well, which provides a heat source;
- a temperature differential mechanical power generation device, which includes a heat source end and a cold source end, the temperature differential mechanical power generation device being disposed in the closed cavity, the heat source end being exposed from the closed cavity and brought into contact with the heat source, and the cold source end being located in the closed cavity;
- an electric power generation device, mechanically connected to the temperature differential mechanical power generation device and housed in the closed cavity, wherein when a temperature difference between the heat source end and the cold source end of the temperature differential mechanical power generation device reaches a specific value, the temperature differential mechanical power generation device mechanically drives the electric power generation device to generate and output electricity;
- a heat conduction module, including a first end and a second end, the first end being located in the closed cavity, and the second end extending out of the well; and
- a heat conduction fluid, filled into the closed cavity, the cold source end of the temperature differential mechanical power generation device, the electric power generation device and the first end of the heat conduction module are immersed in the heat conduction fluid.
2. The subterranean geothermal power generation system of claim 1, wherein the temperature differential mechanical power generation device is a Stirling engine, and the electric power generation device is a linear alternating current generator.
3. The subterranean geothermal power generation system of claim 1, wherein the heat conduction module is at least one selected from the group consisting of a heat pipe, a thermosiphon, a thermal conductive graphite sheet and a vapor chamber.
4. The subterranean geothermal power generation system of claim 1, further comprising a heat dissipation module, which is connected to the second end of the heat conduction module.
5. The subterranean geothermal power generation system of claim 4, wherein the heat dissipation module is exposed to air or immersed in water.
6. The subterranean geothermal power generation system of claim 4, wherein the heat dissipation module is embedded in ground at a depth of 0.5 m to 5 m measured from an earth surface.
7. The subterranean geothermal power generation system of claim 1, further comprising an evacuation module, which is connected to the second end of the heat conduction module, wherein the heat conduction module is a heat pipe, and the evacuation module is used for evacuating the heat pipe.
8. The subterranean geothermal power generation system of claim 7, further comprising a check valve and a negative pressure sensor, wherein the check valve is disposed between the evacuation module and the second end of the heat conduction module, and the negative pressure sensor is used for measuring a negative pressure in the heat conduction module.
9. The subterranean geothermal power generation system of claim 8, further comprising a main controller, a first temperature sensor, a second temperature sensor and a third temperature sensor, wherein the first temperature sensor, the second temperature sensor, the third temperature sensor and the negative pressure sensor are electrically connected to the main controller; the first temperature sensor is disposed at the heat source end of the temperature differential mechanical power generation device; the second temperature sensor is disposed in the closed cavity; the third temperature sensor is disposed at the second end of the heat conduction module.
10. The subterranean geothermal power generation system of claim 1, wherein the closed cavity and the heat conduction module each are externally covered with a heat insulation material.
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Type: Grant
Filed: Jul 29, 2022
Date of Patent: Feb 21, 2023
Assignee: ELAND BLOCKCHAIN FINTECH INC. (San Jose, CA)
Inventor: Ching Song Wu (Taipei)
Primary Examiner: Hoang M Nguyen
Application Number: 17/816,117
International Classification: F03G 4/00 (20060101); H02N 11/00 (20060101); F24T 50/00 (20180101); F24T 10/10 (20180101);